The reproductive lifespan of the woman is largely determined by factors that regulate the number of follicles laid down during fetal development and their subsequent degeneration rate during adult life. Of concern is a possible role of endocrine disrupting chemicals (EDC) in dysregulating the number of follicles or in promoting depletion of the follicle pool. EDCs have been detected in human ovarian follicular fluid. In addition, concentrations of certain EDCs detected in cord blood and amniotic fluid from pregnant women suggest human fetal exposure and the possibility of follicular alterations beginning at an early developmental stage. To date, the literature assessing potential human effects of exposure to environmental EDCs on markers of ovarian reserve, such as anti-mllerian hormone (AMH), is sparse. Our goal is to contribute to current knowledge by conducting secondary analysis of data collected in female adolescents participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) to assess the association of prenatal exposure to PFAS and organochlorine pesticides with AMH concentrations. We will also assess temporal changes in AMH concentrations in relation to these exposures. The ALSPAC is a population-based, birth cohort with a long follow-up period and extensive data collection including the assessment of clinical measures in a large subset of participants. Results of the proposed study will address the rather sparse, existing evidence and support the development of new hypothesis.